Given the scale of my boat and its overall size I had determined months ago that the propeller diameter that was suggested for the completed boat was simply too small for the size of the craft. I decided to go with a larger 70mm diameter brass propeller and once the boat was put in the water for the first time going with that 70mm propeller was the right choice. I also had to enlarge the rudder up to a matching 70 mm rudder brass on a 3/16" brass shaft. The boat runs beautifully and with that prop and rudder combination it turns beautufully even at wide open speeds. Many said that the motor I chose was too large and too heavy at nearly 2 pounds but so far I am very pleased with everything I have assembled.
The completed boat weighs in at 23 pounds (10 Kg.) but you would never know it once it's in the water.